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Simple Constituent Analysis and Quality Evaluation Criteria for Preventing Deterioration of Powdered Green Tea



Author(s)

Satoshi Kanai^1,3, Kojun Tsunoda², Hideo Honma² and Joo-Hyong Noh^1,2

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DOI:10.17265/2161-6213/2026.1-3.004

1. Graduate School of Engineering, Kanto Gakuin University, 1-50-1 Mutsuura-higashi, Kanazawa-ku, Yokohama 236-8501, Kanagawa, Japan
2. Materials & Surface Engineering Research Institute, Kanto Gakuin University, 1-50-1 Mutsuura-higashi, Kanazawa-ku, Yokohama 236-8501, Kanagawa, Japan
3. Ecolo CO., Ltd. 144-3 Jubei, Fuji 416-0941, Shizuoka, Japan

Heat treatment in the green tea manufacturing process converts chlorophyll (Chls: green color) contained in raw tea leaves into pheophytins (Pheos: gray color), which has a significant impact on the appearance quality of the product. In this study, to quantitatively evaluate this thermal discoloration behavior, Chl-a and Pheo-a were separated and analyzed using circular paper chromatography (CPC), which is an omnidirectional diffusion type with a wide separation band suitable for spectroscopic analysis. Using the conversion ratio (Pheo-a/Chl-a) calculated by spectroscopic analysis as an indicator, it was shown that the conversion ratio when boiling fresh tea leaves differed significantly depending on the harvest time and plucking order, and that an increase in this value is a direct factor that promotes the gray-greening of tea leaves. Furthermore, because the discoloration characteristics of commercially available green tea vary depending on the processing method, blending, and the presence or absence of additives, the importance of individual evaluation taking into account the labeled ingredients was confirmed. The evaluation method based on the conversion rate established in this study is expected to contribute to the optimization of the heating process of green tea, quality control, and as an objective indicator for the formulation of quality guidelines for tea leaves.

Green tea, chlorophyll, pheophytin, fading, conversion rate.